Excretion is the process of removal of nitrogenous wastes and metabolic waste like excess salts, phosphates, sulfates, or any excess substances from the body. It plays an important role in maintaining the homeostatic condition of the body. Kidney helps in removal of waste from the body in the form of urine. The skin helps in the removal of wastes in the form of sweat. Lungs excrete carbon dioxide.

Kidneys are the main excretory organ. These are two bean-shaped reddish-brown organs which are found on either side of the vertebral column. It eliminates nitrogenous wastes from the blood and throws it out in the form of urine which contains urea, unwanted salts and excess water. Unit of the kidney is nephron or uriniferous tubules.

Micturition is the process of expelling urine out of the body. Urine is stored in the urinary bladder for a while. When a person gets an urge to secrete it, then relaxation of the sphincter muscles occurs which lets the urine to get expelled out of the body. This is controlled by the nervous system. Urine is formed in the kidneys which is transported to the urinary bladder through ureters.